This invention relates to a suspension system for motorcycles and more particularly to an improved suspension system that permits the achievement of non-linear rates while maintaining a low weight, particularly as to the unsprung components, and which minimizes bending loads on the suspension elements.
The advantages of non-linear vehicular suspension systems have been well known for a period of years. Such suspension systems have particular utility in motorcycles that are intended for off the road racing. In such an application, the use of a non-linear suspension system can offer large degrees of suspension travel with effective damping at the end of the suspension stroke. Although non-linear suspension systems have been readily adapted to rear wheel suspension systems for motorcycles, the use of non-linear suspensions for motorcycle front wheels is not as wide spread. One difficulty in applying non-linear suspensions systems to the front wheels of a motorcycle is that the systems heretofore proposed have significantly increased the unsprung weight of the front wheel. Obviously, such an arrangement can deteriorate the handling of the motorcycle and its riding characteristics. Furthermore, if the system provides sufficient rigidity for the front wheel, it has been found that the internal sliding resistance for the suspension is so high that operation under light loads can be seriously hampered. That is, when operating over a surface that has only small surface irregularities, the hydraulic shock absorber employed in the suspension system may experience cavitation, aeration or the like so as to significantly deteriorate the ride and handling.
It is, therefore, a principal object of this invention to provide a non-linear suspension system, particularly adapted for use in motorcycles, that reduces the unsprung weight.
It is another object of this invention to provide a non-linear motorcycle suspension system that offers high rigidity and reduced unsprung weight.
In the suspension system for a motorcycle front wheel, it is the normal practice to position the steering axis so that it is at a castor angle. When tubular type suspension systems are employed in conjunction with front wheels having a castor angle, the loading on the front wheel tends to create a twisting or bending moment upon the tubular suspension system. The imposition of such bending forces causes substantial resistance to the suspension movement and can result in inferior handling. Although it has been proposed to employ a separate spring that acts upon the front wheel carrier to overcome these bending forces, the use of such springs tends to cause an oversteering effect when turning. Such additional springs complicate the suspension system and add significantly to the unsprung weight. Furthermore, the amount of the bending force can depend upon the actual position of the front wheel in its suspension travel and the springs heretofore employed for resisting these forces do not compensate for the difference in loading.
It is, therefore, a further objection of this invention to provide an improved front suspension system for a motorcycle.
It is yet another object of this invention to provide a telescopic motorcycle front suspension system in which bending forces on the telescopic elements is substantially reduced.